The present invention relates to an endoscopic forceps instrument having a pair of opposed jaws at the distal end thereof.
Typical endoscopic forceps instruments having a pair of opposed jaws include, for example, biopsy forceps, grasping forceps, and hemostatic forceps.
FIG. 1 shows a distal end of a conventional endoscopic forceps instrument 10. The endoscopic forceps instrument 10 includes a clevis 12 coupled to the distal end of a flexible sheath 11. A pair of opposing jaws 14 is pivotably coupled to the distal end of the clevis 12 by a rivet 15. The rivet 15 is inserted into the bores 16 formed to the distal end of the clevis, and extends across the slit 13 of the clevis 12.
A pair of control wires (not shown) are inserted through the sheath 11 and connected to the pair of jaws 14. The pair of opposed jaws 14 open and close if the pair of wires is operated back and forth along the sheath 11 from the proximal end of the endoscopic forceps instrument 10.
The rivet 15 includes a body 15b, a head 15a having larger diameter than a body 15b, and a tip portion 15c having smaller diameter than the body 15b. The tip portion 15c is swaged after the rivet 15 is inserted into the bores 16 of the clevis 12 to fix the rivet 15 to the clevis 12. However, since the mechanical strength of the swaged tip portion 15c of the rivet 15 is relatively low, the rivet 15 comes off from the clevis 15, and hence the distal end of the forceps instrument becomes disassembled, when a large force is exerted on the clevis 15 that acts to widen the slit 13 of the clevis. 
Thus, there is a need for an endoscopic forceps instrument of which the distal end does not readily come apart upon application of a large force.